Method of cleaning substrate processing apparatus

ABSTRACT

A spin base is caused to rotate at a number of revolutions of from 250 rpm to 350 rpm (first number of revolutions), and at the same time, a cleaning solution is supplied through a discharge head to a holding surface of a spin base while the upper end of a processing cup surrounding the spin base is placed below the holding surface. Thus, an outer upper surface of the processing cup is cleaned with the cleaning solution scattered from the holding surface. Then, the spin base is caused to rotate at a number of revolutions of from 350 rpm to 450 rpm (second number of revolutions) higher than the first number of revolutions, and at the same time, a cleaning solution is supplied through the discharge head onto the holding surface. Thus, a partition plate outside the processing cup is cleaned with the cleaning solution scattered from the rotating holding surface.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation under 37 C.F.R. §1.53(b) ofprior application Ser. No. 13/450,654 filed Apr. 19, 2012, by NaoyukiOSADA entitled METHOD OF CLEANING SUBSTRATE PROCESSING APPARATUS andissued as U.S. Pat. No. 9,190,300 on Nov. 17, 2015, which claims benefitand priority of Japanese Application No. JP 2011-099148, filed Apr. 27,2011, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method of cleaning a substrateprocessing apparatus that supplies a processing solution to a precisionelectronic substrate in the form of a thin plate (hereinafter simplycalled a “substrate”) such as a semiconductor water or a glass substratefor a liquid crystal display.

Description of the Background Art

A substrate processing apparatus conventionally employed in a process ofmanufacturing substrates performs surface processing of substratesincluding process with a chemical solution and rising process withde-ionized water, and subsequent drying process. Such a substrateprocessing apparatus includes an apparatus employing a single-wafersystem of processing substrates one by one, and an apparatus employing abatch system of processing a plurality of substrates at the same time.Generally, the substrate processing apparatus of the single-wafer systemperforms process with a chemical solution by supplying a chemicalsolution to a surface of a rotating substrate, rinsing process withde-ionized water by supplying de-ionized water, and subsequentspin-drying process by causing the substrate to rotate at high speed.Such a substrate processing apparatus of the single-water system isdisclosed for example in US 2008/0078428 and in Japanese PatentApplication Laid-Open No. 2010-192686, for example.

The substrate processing apparatus disclosed in these publicationsincludes a spin chuck causing a substrate to rotate held in asubstantially horizontal position thereon, a nozzle from which aprocessing solution is supplied to the upper surface of the substrateheld on the spin chuck, and a cup surrounding the spin chuck andprovided to receive the processing solution scattered from thesubstrate. The apparatus disclosed in Japanese Patent ApplicationLaid-Open No. 2010-192686 additionally includes a processing chamberhousing these components, and a partition plate around the cup providedto divide the processing chamber into parts, one above the other.

This apparatus of the single-wafer system performs surface processing bysupplying a processing solution to a rotating substrate, so theprocessing solution is scattered from the substrate by centrifugalforce. Most of the scattered processing solution is collected in the cupsurrounding the spin chuck. Meanwhile, part of the scattered processingsolution converted into mist form may be scattered as far as to an outerwall surface of the cup or to surroundings of the cup, and then attachedto the outer wall surface or the surroundings of the cup. Thisprocessing solution scattered outside the cup may become a source ofpollution after it is dried.

So, the processing solution attached to the outer wall surface of thecup or to a member around the cup should be cleared where appropriate.The processing solution attached to the part outside the cup may becleared by a special-purpose mechanism such as a nozzle from whichde-ionized water is supplied to the part outside the cup or a nozzlefrom which nitrogen gas is sprayed for drying that is provided inaddition to a nozzle for substrate processing. However, it is difficultto provide such a special-purpose mechanism in a substrate processingapparatus required to be reduced in size.

SUMMARY OF THE INVENTION

The present invention is intended for a method of cleaning a substrateprocessing apparatus that performs substrate processing with aprocessing solution.

According to one aspect of the present invention, the method includesthe following steps (a) and (b). In the step (a), a substrate holdingelement is caused to rotate at a first number of revolutions, thesubstrate holding element having a holding surface facing the lowersurface of a substrate to be held on the substrate holding element, andat the same time, a cleaning solution is supplied from a cleaningsolution supply nozzle onto the holding surface while the upper end of acup surrounding the substrate holding element is placed below thesubstrate holding element, thereby cleaning an outer upper surface ofthe cup with the cleaning solution scattered from the holding surfacewhile the holding surface is rotating. In the step (b), the substrateholding element is caused to rotate at a second number of revolutionshigher than the first number of revolutions, and at the same time, acleaning solution is supplied from the cleaning solution supply nozzleonto the holding surface, thereby cleaning an area outside the cup andsurrounding the cup with the cleaning solution scattered from theholding surface while the holding surface is rotating.

The outer upper surface of the cup and the area outside the cup arecleaned only by a mechanism for performing surface processing on asubstrate, making it possible to clean the upper surface of the cup andsurroundings of the cup without requiring a special-purpose cleaningmechanism.

Preferably, the cleaning solution supply nozzle for supplying a cleaningsolution is caused to move over the holding surface.

This allows the upper surface of the cup and a wide area surrounding thecup to be cleaned favorably.

The method may include the step of drying the outer upper surface of thecup and the area outside the cup with airflow generated by causing thesubstrate holding element to rotate at a fourth number of revolutionshigher than the second number of revolutions. Preferably, in this step,gas is discharged from a gas supply nozzle onto at least the outer uppersurface of the cup.

This allows increase of efficiency of drying.

Thus, an object of the present invention is to clean the upper surfaceof the cup and surroundings of the cup in the substrate processingapparatus without the need of preparing a special-purpose cleaningmechanism.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a substrate processing apparatus targeted forcleaning in a cleaning method of the present invention;

FIG. 2 is a vertical sectional view of the substrate processingapparatus shown in FIG. 1;

FIG. 3 is a flow diagram explaining procedure of the cleaning method ofthe present invention;

FIG. 4 shows the reciprocating movement of an upper processing solutionnozzle;

FIG. 5 shows how an outer upper surface of a processing cup is cleaned;

FIG. 6 shows how a partition plate and a side wall of a chamber arecleaned;

FIG. 7 shows how the inner side of an outer cup is cleaned;

FIG. 8 shows how the inner side of a middle cup is cleaned;

FIG. 9 shows how the inner side of an inner cup is cleaned; and

FIG. 10 shows drying process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention is described in detailbelow by referring to the drawings.

FIG. 1 is a plan view of a substrate processing apparatus 1 targeted forcleaning in a cleaning method of the present invention. FIG. 2 is avertical sectional view of the substrate processing apparatus 1. Thesubstrate processing apparatus 1 is a processing apparatus employing asingle-water system of processing semiconductor substrates W one by one.The substrate processing apparatus 1 performs process with a chemicalsolution and rinsing process with de-ionized water on a circular siliconsubstrate W, and then performs drying process on the substrate W. FIG. 1shows a condition where a substrate W is not held on a spin chuck 20.FIG. 2 shows a condition where a substrate W is held on the spin chuck20.

Main components of the substrate processing apparatus 1 housed in achamber 10 include the spin chuck 20 on which a substrate W is held in ahorizontal position (position that makes the normal of the substrate Wextend in the vertical direction), an upper processing solution nozzle30 through which a processing solution is supplied onto the uppersurface of the substrate W held on the spin chuck 20, and a processingcup 40 surrounding the spin chuck 20. A partition plate 15 is providedaround the processing cup 40 in the chamber 10. The partition plate 15divides the space inside the chamber 10 into parts, one above the other.In the present specification, a processing solution is a generic termfor a chemical solution and de-ionized water.

The chamber 10 has a side wall 11 extending in the vertical direction, aceiling wall 12 enclosing space from above surrounded by the side wall11, and a floor wall 13 enclosing the space from below. The spacesurrounded by the side wall 11, the ceiling wall 12, and the floor wall13 functions as processing space for a substrate W. Further, part of theside wall 11 of the chamber 10 is given a port through which a substrateW is transferred into the chamber 10 and out of the chamber 10, and ashutter to open and close the port (both the port and the shutter arenot shown in the drawings).

The ceiling wall 12 of the chamber 10 is provided with a fan filter unit(FFU) 14 that improves the cleanness of air in a clean room in which thesubstrate processing apparatus 1 is placed, and supplies the cleaned airinto the processing space in the chamber 10. The fan filter unit 14includes a fan for taking the air inside the clean room and feeding theair into the chamber 10, and a filter (such as a HEPA filter), and formsa downflow of the cleaned air in the processing space in the chamber 10.A punching plate with many blowholes may be provided directly below theceiling wall 12 in order to realize uniform distribution of the cleanedair supplied from the fan filter unit 14.

The spin chuck 20 includes a spin base 21 in the form of a circular diskfixed in a horizontal position to the upper end of a rotary shaft 24extending in the vertical direction, a spin motor 22 provided below thespin base 21 and which causes the rotary shaft 24 to rotate, and acylindrical cover member 23 surrounding the spin motor 22. The outerdiameter of the spin base 21 in the form of a circular disk is slightlylarger than the diameter of a circular substrate W held on the spinchuck 20. So, a holding surface 21 a of the spin base 21 is to face theentire lower surface of a substrate W to be held on the spin base 21.

A plurality of (in the preferred embodiment, four) chuck members 26 isprovided in upright positions at peripheral edges of the holding surface21 a of the spin base 21. The chuck members 26 are uniformly spaced (iffour chuck members 26 are provided as in the preferred embodiment, theyare spaced at intervals of 90 degrees) along a circumferencecorresponding to the outer circumference of a circular substrate W. Thechuck members 26 are driven in synchronization with each other by a linkmechanism not shown in the drawings housed in the spin base 21. The spinchuck 20 makes abutting contact of each of the chuck members 26 with acorresponding peripheral edge to grasp a substrate W, thereby holdingthe substrate W in a horizontal position above the spin base 21 and nearthe holding surface 21 a (see FIG. 2). The spin chuck 20 also separateseach of the chuck members 26 from a corresponding peripheral edge of thesubstrate W, thereby releasing the substrate W from the grasp.

The cover member 23 covering the spin motor 22 has a lower end fixed tothe floor wall 13 of the chamber 10, and an upper end reaching as far asto a position directly below the spin base 21. An upper end portion ofthe cover member 23 is provided with a flange member 25 projecting in asubstantially horizontal position outward of the cover member 23, andfurther being downward. While the spin chuck 20 holds a substrate W bycausing the chuck members 26 to grasp the substrate W, the spin motor 22causes the rotary shaft 24 to rotate, thereby allowing the substrate Wto rotate about an axis of rotation CX extending in the verticaldirection and passing through the center of the substrate W. Acontroller 9 controls drive of the spin motor 22.

The upper processing solution nozzle 30 is composed of a nozzle arm 32,and a discharge head 31 attached to the tip end of the nozzle arm 32.The base end of the nozzle arm 32 is fixedly coupled to a nozzle base33. A motor not shown in the drawings allows pivotal movement of thenozzle base 33 about an axis extending in the vertical direction. Thepivotal movement of the nozzle base 33 causes the discharge head 31 ofthe upper processing solution nozzle 30 to move horizontally in anarcuate pattern between a processing position over the spin chuck 20 anda standby position outside the processing cup 40. The upper processingsolution nozzle 30 is configured to receive processing solutions ofseveral types (including at least de-ionized water). A processingsolution discharged at the processing position through the dischargehead 31 of the upper processing solution nozzle 30 reaches the uppersurface of a substrate W held on the spin chuck 20. Further, the pivotalmovement of the nozzle base 33 allows the upper processing solutionnozzle 30 to swing over the holding surface 21 a of the spin base 21.

A lower processing solution nozzle 28 is provided that extends in thevertical direction inside the rotary shaft 24. An opening at the upperend of the lower processing solution nozzle 28 is placed at a positionopposite the center of the lower surface of a substrate W held on thespin chuck 20. The lower processing solution nozzle 28 is alsoconfigured to receive processing solutions of several types. Aprocessing solution discharged from the lower processing solution nozzle28 reaches the lower surface of a substrate W held on the spin chuck 20.

The substrate processing apparatus 1 includes a two-fluid nozzle 60 inaddition to the upper processing solution nozzle 30. The two-fluidnozzle 60 is a cleaning nozzle that generates droplets by mixing acleaning solution such as de-ionized water and pressurized gas, andsprays the mixed fluid of the droplets and the gas onto a substrate W.The two-fluid nozzle 60 has a liquid head not shown in the drawingsattached to the tip end of a nozzle arm 62, and a gas head 64 attachedto a support member branching off the nozzle arm 62. The base end of thenozzle arm 62 is fixedly coupled to a nozzle base 63. A motor not shownin the drawings allows pivotal movement of the nozzle base 63 about anaxis extending in the vertical direction. The pivotal movement of thenozzle base 63 causes the two-fluid nozzle 60 to move horizontally in anarcuate pattern between a processing position above the spin chuck 20and a standby position outside the processing cup 40. The liquid headreceives a cleaning solution such as de-ionized water, and the gas head64 receives a pressurized inert gas (in the preferred embodiment,nitrogen (N₂) gas). A mixed fluid of a cleaning solution spouted out ofthe two-fluid nozzle 60 at the processing position is sprayed onto theupper surface of a substrate W held on the spin chuck 20.

The processing cup 40 surrounding the spin chuck 20 includes an innercup 41, a middle cup 42, and an outer cup 43 that are capable of movingup and down independently of each other. The inner cup 41 has a shapesurrounding the spin chuck 20, and exhibiting substantially rotationalsymmetry about the axis of rotation CX passing through the center of asubstrate W held on the spin chuck 20. The inner cup 41 has a bottomsection 44 having a toroidal shape in plan view, a cylindrical innerwall section 45 extending upward from an inner periphery of the bottomsection 44, a cylindrical outer wall section 46 extending upward from anouter periphery of the bottom section 44, a first guide section 47extending upward from a position between the inner and outer wallsections 45 and 46 and having an upper end portion that extendsobliquely upward in the pattern of a smooth circular arc toward thecenter (in a direction to get closer to the axis of rotation CX of asubstrate W held on the spin chuck 20), and a cylindrical middle wallsection 48 extending upward from a position between the first guidesection 47 and the outer wall section 46.

The inner wall section 45 has a length that places the inner wallsection 45 between the cover member 23 and the flange member 25 withappropriate clearance left therebetween when the inner cup 41 is at itshighest position (see FIG. 9). The middle wall section 48 has a lengththat places the middle wall section 48 between a second guide section 52of the middle cup 42 and a processing solution dividing wall 53described later with appropriate clearance left therebetween when theinner and middle cups 41 and 42 are at their closest positions.

The first guide section 47 has an upper end portion 47 b that extendsobliquely upward in the pattern of a smooth circular arc toward thecenter (in a direction to get closer to the axis of rotation CX of asubstrate W). A disposal slot 49 is formed between the inner wallsection 45 and the first guide section 47 in which a used processingsolution is collected and disposed of A toroidal inner recovery slot 50is formed between the first guide section 47 and the middle wall section48 in which a used processing solution is collected and recovered. Also,a toroidal outer recovery slot 51 is formed between the middle and outerwall sections 48 and 46 in which a used processing solution of a typedifferent from that collected in the inner recovery slot 50 is collectedand recovered.

The disposal slot 49 discharges a processing solution collected in thedisposal slot 49. The disposal slot 49 is connected to a dischargemechanism not shown in the drawings that forcibly extracts air from thedisposal slot 49. As an example, four discharge mechanisms are providedthat are uniformly spaced in the circumferential direction of thedisposal slot 49. Further, recovery mechanisms (both of which are notshown in the drawings) are connected to the inner and outer recoveryslots 50 and 51 by which processing solutions collected in the inner andouter recovery slots 50 and 51 respectively are recovered in a recoverytank provided outside the substrate processing apparatus 1. Respectivebottom portions of the inner and outer recovery slots 50 and 51 aretilted at slight angles with respect to the horizontal direction, andthe respective recovery mechanisms are connected to the lowest positionsof the bottom portions. This allows smooth recovery of processingsolutions flowing into the inner and outer recovery slots 50 and 51.

The middle cup 42 has a shape surrounding the spin chuck 20, andexhibiting substantially rotational symmetry about the axis of rotationCX passing through the center of a substrate W held on the spin chuck20. The middle cup 42 has the integrally formed second guide section 52,and the cylindrical processing solution dividing wall 53 coupled to thesecond guide section 52.

The second guide section 52 is placed outside the first guide section 47of the inner cup 41. The second guide section 52 has a cylindrical lowerend portion 52 a coaxial with a lower end portion of the first guidesection 47, an upper end portion 52 b extending obliquely upward fromthe upper end of the lower end portion 52 a in the pattern of a smoothcircular arc toward the center (in a direction to get closer to the axisof rotation CX of a substrate W), and a bent portion 52 c formed bybending the tip end of the upper end portion 52 b downward. The lowerend portion 52 a is placed in the inner recovery slot 50 withappropriate clearance left between the first guide section 47 and themiddle wall section 48 when the inner and middle cups 41 and 42 are attheir closest positions. The upper end portion 52 b is arranged to coverthe upper end portion 47 b of the first guide section 47 of the innercup 41 from above. The upper end portion 52 b is close to the upper endportion 47 b of the first guide section 47 with slight clearance lefttherebetween when the inner and middle cups 41 and 42 are at theirclosest positions. The bent portion 52 c formed by bending the tip endof the upper end portion 52 b downward has a length that makes the bentportion 52 c cover the tip end of the upper end portion 47 b of thefirst guide section 47 from the side when the inner and middle cups 41and 42 are at their closest positions.

The upper end portion 52 b of the second guide section 52 becomesthicker with approach toward its bottom. The processing solutiondividing wall 53 has a cylindrical shape extending downward from aperipheral portion at the lower end of the upper end portion 52 b. Theprocessing solution dividing wall 53 is placed in the outer recoveryslot 51 with appropriate clearance left between the middle wall section48 and the outer cup 43 when the inner and middle cups 41 and 42 are attheir closest positions.

The outer cup 43 is provided outside the second guide section 52 of themiddle cup 42. The outer cup 43 has a shape surrounding the spin chuck20, and exhibiting substantially rotational symmetry about the axis ofrotation CX passing through the center of a substrate W held on the spinchuck 20. The outer cup 43 functions as a third guide section. The outercup 43 has a cylindrical lower end portion 43 a coaxial with the lowerend portion 52 a of the second guide section 52, an upper end portion 43b extending obliquely upward from the upper end of the lower end portion43 a in the pattern of a smooth circular arc toward the center (in adirection to get closer to the axis of rotation CX of a substrate W),and a bent portion 43 c formed by bending the tip end of the upper endportion 43 b downward.

The lower end portion 43 a is placed in the outer recovery slot 51 withappropriate clearance left between the processing solution dividing wall53 of the middle cup 42 and the outer wall section 46 of the inner cup41 when the inner and outer cups 41 and 43 are at their closestpositions. The upper end portion 43 b is arranged to cover the secondguide section 52 of the middle cup 42 from above. The upper end portion43 b is close to the upper end portion 52 b of the second guide section52 with slight clearance left therebetween when the middle and outercups 42 and 43 are at their closest positions. The bent portion 43 cformed by bending the tip end of the upper end portion 43 b downward hasa length that makes the bent portion 43 c cover the bent portion 52 c ofthe second guide section 52 from the side when the middle and outer cups42 and 43 are at their closest positions.

The inner, middle and outer cups 41, 42 and 43 are capable of moving upand down independently of each other. To be specific, the inner, middleand outer cups 41, 42 and 43 are given their respective liftingmechanisms (not shown in the drawings) that move corresponding ones ofthe inner, middle and outer cups 41, 42 and 43 up and down separately.Various publicly known mechanisms such as a ball screw mechanism and anair cylinder may be employed as these lifting mechanisms.

The partition plate 15 divides the space inside the chamber 10 andsurrounding the processing cup 40 into parts, one above the other. Thepartition plate 15 may be a single plate-like member surrounding theprocessing cup 40, or may be formed by joining a plurality of plate-likemembers together. Also, the partition plate 15 may be given a throughhole passing through the partition plate 15 in the thickness directionor a notch. In the preferred embodiment, the partition plate 15 is giventhrough holes causing support shafts to pass therethrough that supportthe nozzle bases 33 and 63 of the upper processing solution nozzle 30and the two-fluid nozzle 60 respectively.

The outer circumferential edge of the partition plate 15 is coupled tothe side wall 11 of the chamber 10. A peripheral portion of thepartition plate 15 surrounding the processing cup 40 has a circularshape of a diameter larger than the outer diameter of the outer cup 43.So, the partition plate 15 will not prevent up and down movement of theouter cup 43.

An exhaust duct 18 is provided to part of the side wall 11 of thechamber 10 and at a position near the floor wall 13. The exhaust duct 18is communicatively connected to an exhaust mechanism not shown in thedrawings. Clean air is supplied from the fan filter unit 14 to flow downinside the chamber 10, and part of the clean air after passing throughspace between the processing cup 40 and the partition plate 15 is drawnout of the substrate processing apparatus 1 through the exhaust duct 18.

The hardware structure of the controller 9 in the substrate processingapparatus 1 is the same as that of a generally used computer. To bespecific, the controller 9 includes a CPU responsible for variousarithmetic operations, a ROM that is a read-only memory storing a basicprogram, a RAM that is a memory from and into which various informationcan be read and written freely, a magnetic disk storing control softwareand data, and the like. Execution of a predetermined processing programby the CPU of the controller 9 makes the controller 9 control eachoperating mechanism of the substrate processing apparatus 1, therebyrealizing processing in the substrate processing apparatus 1.

The operation of the substrate processing apparatus 1 having theaforementioned structure is described next. Procedure generally taken bythe substrate processing apparatus 1 to process a substrate W brieflyincludes predetermined process with a chemical solution by supplying achemical solution onto a surface of the substrate W, subsequent rinsingprocess with de-ionized water by supplying de-ionized water, and thensubsequent spin-drying process by causing the substrate W to rotate athigh speed. For processing of the substrate W, the substrate W is heldon the spin chuck 20, and the processing cup 40 moves up and down. Byway of example, for process with a chemical solution, only the outer cup43 moves up to form an opening surrounding the substrate W held on thespin chuck 20 between the upper end portion 43 b of the outer cup 43 andthe second guide section 52 of the middle cup 42 (see FIG. 7). In thiscondition, the substrate W is caused to rotate together with the spinchuck 20 while chemical solutions are supplied onto the upper and lowersurfaces of the substrate W through the upper and lower processingsolution nozzles 30 and 28 respectively. The chemical solutions therebysupplied are caused to flow over the upper and lower surfaces of thesubstrate W by centrifugal force generated by the rotation of thesubstrate W, and then scattered laterally from the peripheral edgeportion of the substrate W, by which the process with a chemicalsolution of the substrate W proceeds. The chemical solutions scatteredfrom the peripheral edge portion of the rotating substrate W arereceived by the upper end portion 43 b of the outer cup 43, pass throughthe inner surface of the outer cup 43, and are then recovered in theouter recovery slot 51.

For rinsing process with de-ionized water, all the inner, middle andouter cups 41, 42 and 43 move up, for example, so that a substrate Wheld on the spin chuck 20 is surrounded by the first guide section 47 ofthe inner cup 41 (see FIG. 9). In this condition, the substrate W iscaused to rotate together with the spin chuck 20 while de-ionized wateris supplied onto the upper and lower surfaces of the substrate W fromthe upper and lower processing solution nozzles 30 and 28 respectively.The de-ionized water thereby supplied is caused to flow over the upperand lower surfaces of the substrate W by centrifugal force generated bythe rotation of the substrate W, and then scattered laterally from theperipheral edge portion of the substrate W, by which the rising processwith de-ionized water of the substrate W proceeds. The de-ionized waterscattered from the peripheral edge portion of the rotating substrate Wflows down along the inner wall of the first guide section 47, and thendischarged through the disposal slot 49. In order for de-ionized waterto be recovered in a path different from the path of recovery of achemical solution, the middle and outer cups 42 and 43 may be caused tomove up to form an opening surrounding a substrate W held on the spinchuck 20 between the upper end portion 52 b of the second guide section52 of the middle cup 42 and the upper end portion 47 b of the firstguide section 47 of the inner cup 41 (see FIG. 8).

For spin-drying process, all the inner, middle and outer cups 41, 42 and43 move down to place each of the upper end portion 47 b of the firstguide section 47 of the inner cup 41, the upper end portion 52 b of thesecond guide section 52 of the middle cup 42, and the upper end portion43 b of the outer cup 43 below a substrate W held on the spin chuck 20.In this condition, the substrate W is caused to rotate together with thespin chuck 20 at high speed to blow water droplets off the substrate Wby using centrifugal force, thereby realizing the drying process.

In the aforementioned surface processing realized by supplying aprocessing solution onto a substrate W, while most of the processingsolution scattered from the rotating substrate W is recovered in theprocessing cup 40, part of the processing solution is converted intomist form and such processing solution in mist form may be scattered asfar as to the outside of the processing cup 40. The processing solutionscattered outside of the processing cup 40 reaches as far as the outerupper surface of the processing cup 40 or the partition plate 15, and isthen attached to the outer upper surface or the partition plate 15. Theouter upper surface of the processing cup 40 mentioned here correspondsto an outer upper surface 43 d of the upper end portion 43 b of theouter cup 43 in the outermost position. The processing solution attachedto the outer upper surface 43 d of the processing cup 40 or the uppersurface of the partition plate 15 may become a source of pollution as itmay generate particles and the like after being dried.

So, in the preferred embodiment, the outer upper surface 43 d of theprocessing cup 40 and the upper surface of the partition plate 15 arecleaned in the following manner. FIG. 3 is a flow diagram explainingprocedure of the cleaning method of the present invention. Cleaningprocess of the preferred embodiment is performed when there is nosubstrate W in the substrate processing apparatus 1, and is preferablyperformed at a time during an interval between processing lots.

First, the outer upper surface 43 d of the processing cup 40 is cleaned(step S1). While there is no substrate W in the substrate processingapparatus 1, namely while there is no substrate W held on the spin chuck20, all the inner, middle and outer cups 41, 42 and 43 move down totheir lowest positions. This places each of the upper end portion 47 bof the first guide section 47 of the inner cup 41, the upper end portion52 b of the second guide section 52 of the middle cup 42, and the upperend portion 43 b of the outer cup 43 below the holding surface 21 a ofthe spin base 21 of the spin chuck 20 (corresponding to the condition ofFIG. 2). In this condition, the spin base 21 of the spin chuck 20 isdriven by the spin motor 22 to rotate about the axis of rotation CX. Thenumber of revolutions of the spin base 21 in step S1 is from 250 rpm to350 rpm (first number of revolutions), and this number of revolutions iscontrolled by the controller 9.

The upper end of the processing cup 40 (upper end portions 47 b, 52 band 43 b) is placed below the holding surface 21 a of the spin base 21while the spin base 21 is caused to rotate at a number of revolutions offrom 250 rpm to 350 rpm. Further, the nozzle base 33 of the upperprocessing solution nozzle 30 causes the nozzle arm 32 to pivot to movethe discharge head 31 to a position above the spin base 21. Then, acleaning solution (in the preferred embodiment, de-ionized water) issupplied through the discharge head 31 onto the holding surface 21 a ofthe rotating spin base 21.

At this time, the nozzle base 33 makes swinging movement of the nozzlearm 32 under control of the controller 9 to cause the discharge head 31supplying de-ionized water to move back and forth over the spin base 21as shown in FIG. 4. As an example, this reciprocating movement is madeby causing the discharge head 31 to move repeatedly between one edge andthe opposite edge of the spin base 21 in the form of a circular plate inthe direction of the diameter thereof. This reciprocating movement isnot limited to continuous reciprocating movement where the dischargehead 31 is caused to move continuously. This reciprocating movement mayalso be intermittent reciprocating movement where the discharge head 31moves to the opposite edge and stops for a while there after stopping atthe one edge for a while, and then moves back to the one edge and stopsthere for a while.

In response to supply of de-ionized water onto the holding surface 21 aof the rotating spin base 21, the de-ionized water is scatteredlaterally from the peripheral edge portion of the holding surface 21 aby centrifugal force. The upper end of the processing cup 40 is placedbelow the holding surface 21 a of the spin base 21, so the de-ionizedwater scattered from the rotating holding surface 21 a falls onto theouter upper surface 43 d of the processing cup 40 (more specifically,the outer upper surface 43 d of the outer cup 43) as shown in FIG. 5.Falling of the scattered de-ionized water washes away a processingsolution attached to the outer upper surface 43 d of the processing cup40 to clean the outer upper surface 43 d.

If the discharge head 31 is above one edge of the spin base 21 in thedirection of the diameter thereof, a large amount of de-ionized waterfalls onto the outer upper surface 43 d of the processing cup 40 in aregion close to the one edge to clean this region favorably. Meanwhile,if the discharge head 31 is above the opposite edge of the spin base 21,a large amount of de-ionized water falls onto the outer upper surface 43d of the processing cup 40 in a region close to the opposite edge toclean this region favorably. Thus, the reciprocating movement of thedischarge head 31 of the upper processing solution nozzle 30 over thespin base 21 makes it possible to clean the entire outer upper surface43 d of the processing cup 40 favorably.

The partition plate 15 and the side wall 11 of the chamber 10 arecleaned (step S2) after the outer upper surface 43 d of the processingcup 40 is cleaned. In this step, while all the inner, middle and outercups 41, 42 and 43 are also at their lowest positions around the spinchuck 20 on which no substrate W is held, the spin base 21 rotates aboutthe axis of rotation CX. The number of revolutions of the spin base 21in step S2 is from 350 rpm to 450 rpm (second number of revolutions)higher than the first number of revolutions of step S1. This means thatthe controller 9 only increases the number of revolutions of the spinbase 21 in order to make a transition from step S1 to step S2.

The upper end of the processing cup 40 (upper end portions 47 b, 52 band 43 b) is placed below the holding surface 21 a of the spin base 21.In this condition, de-ionized water is supplied through the dischargehead 31 onto the holding surface 21 a while the spin base 21 is causedto rotate at a number of revolutions of from 350 rpm to 450 rpm. At thistime, like in step S1, the discharge head 31 supplying de-ionized wateris caused to move back and forth over the spin base 21.

In response to supply of de-ionized water onto the holding surface 21 aof the rotating spin base 21, the de-ionized water is scatteredlaterally from the peripheral edge portion of the holding surface 21 aby centrifugal force. The upper end of the processing cup 40 is placedbelow the holding surface 21 a of the spin base 21, and the spin base 21rotates at a number of revolutions higher than that employed in cleaningof the upper surface of the cup in step S1, so greater centrifugal forceacts on the de-ionized water. As a result, the de-ionized waterscattered from the rotating holding surface 21 a travels a longerdistance than that of step S1 to fall onto the upper surface of thepartition plate 15 and the side wall 11 of the chamber 10 as shown inFIG. 6. Falling of the de-ionized water scattered from the spin base 21cleans the upper surface of the partition plate 15 and the side wall 11of the chamber 10.

Like in the cleaning of the upper surface of the cup in step S1, if thedischarge head 31 is above one edge of the spin base 21 in the directionof the diameter thereof, a large amount of de-ionized water falls ontothe partition plate 15 and the side wall 11 in a region close to the oneedge. Meanwhile, if the discharge head 31 is above the opposite edge ofthe spin base 21, a large amount of de-ionized water falls onto thepartition plate 15 and the side wall 11 in a region close to theopposite edge. Thus, the reciprocating movement of the discharge head 31over the spin base 21 makes it possible to clean the entire uppersurface of the partition plate 15 and the entire side wall 11 of thechamber 10 favorably.

Next, the inner side of the processing cup 40 is cleaned (step S3). Theprocessing cup 40 includes the inner, middle and outer cups 41, 42 and43 that are capable of moving up and down independently of each other.The respective inner surfaces of the inner, middle and outer cups 41, 42and 43 function as guide sections. To be specific, the processing cup 40includes a plurality of guides sections extending in the direction ofthe height of the processing cup 40. For cleaning of the inner side ofthe cup, the outer cup 43, the middle cup 42, and the inner cup 41 moveup sequentially around the spin chuck 20 on which no substrate W isheld. Then, the spin base 21 of the spin chuck 20 is driven by the spinmotor 22 to rotate about the axis of rotation CX. The number ofrevolutions of the spin base 21 in step S3 is from 100 rpm to 200 rpm(third number of revolutions) smaller than the first number ofrevolutions of step S1.

For cleaning of the inner side of the outer cup 43, only the outer cup43 moves up as shown in FIG. 7. This places the upper end portion 43 bof the outer cup 43 above the holding surface 21 a of the spin base 21to form an opening surrounding the holding surface 21 a of the spin base21 between the upper end portion 43 b of the outer cup 43 and the upperend portion 52 b of the middle cup 42. Thus, the outer cup 43functioning as the third guide section surrounds the holding surface 21a of the spin base 21 at the same height as the holding surface 21 a. Inthis condition, de-ionized water is supplied through the discharge head31 onto the holding surface 21 a while the spin base 21 is caused torotate at a number of revolutions of from 100 rpm to 200 rpm. Further,like in steps S1 and S2 described above, the discharge head 31 supplyingde-ionized water is caused to move back and forth over the spin base 21.

Supplying de-ionized water through the discharge head 31 onto theholding surface 21 a while causing the spin base 21 to rotate generatescentrifugal force, and this centrifugal force scatters the de-ionizedwater from the peripheral edge portion of the holding surface 21 atoward the inner side of the outer cup 43. As shown in FIG. 7, thede-ionized water scattered from the holding surface 21 a of the spinbase 21 falls onto the inner surface of the outer cup 43, and at thesame time, onto the outer upper surface of the middle cup 42, therebycleaning the inner surface of the outer cup 43 and the outer uppersurface of the middle cup 42. Like in the aforementioned cases, thereciprocating movement of the discharge head 31 over the spin base 21makes it possible to clean the entire inner side of the outer cup 43favorably.

For cleaning of the inner side of the middle cup 42, the outer andmiddle cups 43 and 42 move up (only the inner cup 41 is at a lowerposition) as shown in FIG. 8. This places the upper end portion 43 b ofthe outer cup 43 and the upper end portion 52 b of the middle cup 42above the holding surface 21 a of the spin base 21 to form an openingsurrounding the holding surface 21 a of the spin base 21 between theupper end portion 52 b of the middle cup 42 and the upper end portion 47b of the inner cup 41. Thus, the second guide section 52 of the middlecup 42 surrounds the holding surface 21 a of the spin base 21 at thesame height as the holding surface 21 a. In this condition, de-ionizedwater is supplied through the discharge head 31 onto the holding surface21 a while the spin base 21 is caused to rotate at a number ofrevolutions of from 100 rpm to 200 rpm. Further, like in theaforementioned cases, the discharge head 31 supplying de-ionized wateris caused to move back and forth over the spin base 21.

Supplying de-ionized water through the discharge head 31 onto theholding surface 21 a while causing the spin base 21 to rotate generatescentrifugal force, and this centrifugal force scatters the de-ionizedwater from the peripheral edge portion of the holding surface 21 atoward the inner side of the middle cup 42. As shown in FIG. 8, thede-ionized water scattered from the holding surface 21 a of the spinbase 21 falls onto the inner surface of the middle cup 42, and at thesame time, onto the outer upper surface of the inner cup 41, therebycleaning the inner surface of the middle cup 42 (second guide section52) and the outer upper surface of the inner cup 41. Further, thereciprocating movement of the discharge head 31 over the spin base 21makes it possible to clean the entire inner side of the middle cup 42favorably.

For cleaning of the inner side of the inner cup 41, all the outer,middle and inner cups 43, 42 and 41 move up as shown in FIG. 9. Thisplaces all of the upper end portion 43 b of the outer cup 43, the upperend portion 52 b of the middle cup 42, and the upper end portion 47 b ofthe inner cup 41 above the holding surface 21 a of the spin base 21 tomake the first guide section 47 of the inner cup 41 surround the holdingsurface 21 a of the spin base 21 at the same height as the holdingsurface 21 a. In this condition, de-ionized water is supplied throughthe discharge head 31 onto the holding surface 21 a while the spin base21 is caused to rotate at a number of revolutions of from 100 rpm to 200rpm. Further, the discharge head 31 supplying de-ionized water is causedto move back and forth over the spin base 21.

Supplying de-ionized water through the discharge head 31 onto theholding surface 21 a while causing the spin base 21 to rotate generatescentrifugal force, and this centrifugal force scatters the de-ionizedwater from the peripheral edge portion of the holding surface 21 atoward the inner side of the inner cup 41. As shown in FIG. 9, thede-ionized water scattered from the holding surface 21 a of the spinbase 21 falls onto the inner surface of the inner cup 41 (first guidesection 47), thereby cleaning the inner surface of the inner cup 41.Further, the reciprocating movement of the discharge head 31 over thespin base 21 makes it possible to clean the entire inner side of theinner cup 41 favorably.

As described above, in step S3, the three guide sections formed of therespective inner surfaces of the inner, middle and outer cups 41, 42 and43 are cleaned while these guide sections are placed at the same heightas the holding surface 21 a of the spin base 21.

Drying process (step S4) follows the aforementioned cleaning process ofthe inner side of the processing cup 40. For the drying process, like insteps S1 and S2, all the inner, middle and outer cups 41, 42 and 43 movedown to their lowest positions to place the upper end of the processingcup 40 (upper end portions 47 b, 52 b and 43 b) below the holdingsurface 21 a of the spin base 21. Further, the discharge head 31 of theupper processing solution nozzle 30 moves to the standby positionoutside the processing cup 40. In this condition, the spin base 21 ofthe spin chuck 20 is driven by the spin motor 22 to rotate at high speedabout the axis of rotation CX. The number of revolutions of the spinbase 21 during the drying process in step S4 is about 2500 rpm (fourthnumber of revolutions) considerably higher than the second number ofrevolutions of step S2.

FIG. 10 shows the drying process realized by the rotation of the spinbase 21. The spin base 21 with the chuck members 26 provided atperipheral edges of the holding surface 21 a rotates at high speed togenerate spiral airflow in the chamber 10. The airflow generated as aresult of the rotation of the spin base 21 is sprayed to dry the outerupper surface 43 d of the processing cup 40, the upper surface of thepartition plate 15, and the side wall 11 of the chamber 10.

An inert gas (in the preferred embodiment, nitrogen (N₂) gas) is sprayedfrom the two-fluid nozzle 60 onto the outer upper surface 43 d of theprocessing cup 40 while the spin base 21 rotates. At this time, liquidis not supplied to the two-fluid nozzle 60 but the inert gas is suppliedto the gas head 64 to discharge only the inert gas through the gas head64. Further, the nozzle base 63 of the two-fluid nozzle 60 may make thenozzle arm 62 swing to move the gas head 64 through which the inert gasis sprayed over the processing cup 40 and the partition plate 15. Theairflow generated by the rotation of the spin base 21 and spray of theinert gas through the two-fluid nozzle 60 make it possible to dry theouter upper surface 43 d of the processing cup 40 and the partitionplate 15 at enhanced efficiency.

In the preferred embodiment, the spin base 21 of the spin chuck 20 iscaused to rotate at a number of revolutions of from 250 rpm to 350 rpm(first number of revolutions), and at the same time, a cleaning solutionis supplied from the upper processing solution nozzle 30 onto theholding surface 21 a while the upper end of the processing cup 40surrounding the spin base 21 is placed below the holding surface 21 a ofthe spin base 21. The outer upper surface 43 d of the processing cup 40is cleaned with the cleaning solution scattered from the holding surface21 a of the rotating spin base 21.

Further, the spin base 21 is caused to rotate at a number of revolutionsof from 350 rpm to 450 rpm (second number of revolutions) higher thanthe first number of revolutions, and at the same time, a cleaningsolution is supplied from the upper processing solution nozzle 30 ontothe holding surface 21 a of the spin base 21. The partition plate 15 andthe side wall 11 of the chamber 10 outside the processing cup 40 arecleaned with the cleaning solution scattered from the rotating holdingsurface 21 a.

The components of the substrate processing apparatus 1 including thespin chuck 20, the processing cup 40, and the upper processing solutionnozzle 30 are all originally intended to perform surface processing on asubstrate W, and the operations thereof are based on the assumption thata substrate W is held on the spin chuck 20. To be specific, thesecomponents provided in the chamber 10 are not intended to clean a memberother than a substrate W.

In the preferred embodiment, while the spin chuck 20 on which asubstrate W is not held is caused to rotate, a cleaning solution issupplied from the upper processing solution nozzle 30 onto the holdingsurface 21 a of the spin base 21. The cleaning solution scattered fromthe rotating spin base 21 by resultant centrifugal force is used toclean the outer upper surface 43 d of the processing cup 40, thepartition plate 15, and the side wall 11 of the chamber 10. This meansthat the preferred embodiment makes it possible to clean the outer uppersurface 43 d of the processing cup 40 and surroundings of the processingcup 40 without requiring a special-purpose cleaning mechanism.

Also, in the preferred embodiment, a target of cleaning can be changedfrom the outer upper surface 43 d of the processing cup 40 to an areaoutside the processing cup 40 and surrounding the processing cup 40 bymerely causing the controller 9 to control the number of revolutions ofthe spin base 21. Thus, the outer upper surface 43 d of the processingcup 40 and the surroundings of the processing cup 40 can be cleanedsequentially without the need of specifically preparing aspecial-purpose mechanism. During cleaning of the inner side of theprocessing cup 40 in step S3, inner and outer surfaces of two adjacentcups placed one above the other can be cleaned sequentially by makingfine control of the number of revolutions of the spin base 21. As anexample, increasing the number of revolutions of the spin base 21 in thecondition shown in FIG. 7 makes it possible to change a target ofcleaning from the outer upper surface of the middle cup 42 to the innersurface of the outer cup 43. Likewise, increasing the number ofrevolutions of the spin base 21 in the condition shown in FIG. 8 makesit possible to change a target of cleaning from the outer upper surfaceof the inner cup 41 to the inner surface of the middle cup 42.

The present invention is not limited to the preferred embodimentdescribed above, but various modifications thereof can be made withoutdeparting from the substance of the present invention. As an example,the preferred embodiment uses de-ionized water as a cleaning solutionused in steps S1 to S3. However, de-ionized water is not the onlyexample of a cleaning solution, but a cleaning solution may also be asolution formed by diluting a chemical solution with de-ionized water.

In the preferred embodiment described above, the upper processingsolution nozzle 30 is used as a nozzle for supplying a cleaning solutiononto the holding surface 21 a of the spin base 21. Meanwhile, thetwo-fluid nozzle 60 may take the place of the upper processing solutionnozzle 30 to supply a cleaning solution to the spin base 21 in steps S1to S3. The two-fluid nozzle 60 is also originally provided to performsurface processing on a substrate W, and is not intended to clean amember other than a substrate W.

In step S2, the number of revolutions of the spin base 21 is increasedto clean the partition plate 15 and the side wall 11 of the chamber 10.Meanwhile, components existing between the processing cup 40 and theside wall 11 can also be cleaned in the absence of the partition plate15. To be specific, what should be done in step S2 is to clean an areaoutside the processing cup 40 and surrounding the processing cup 40 witha cleaning solution scattered from the holding surface 21 a of therotating spin base 21.

Further, in the preferred embodiment described above, the processing cup40 includes the inner, middle and outer cups 41, 42 and 43 that arecapable of moving up and down independently of each other. Meanwhile,the processing cup 40 may alternatively include integrally formed threecups that make up and movements. If integrally formed three cups areplaced one above the other at several stages, these cups maysequentially move up and down to surround the holding surface 21 a ofthe spin base 21 in step S3. Or, the processing cup 40 may include a cuponly at one stage surrounding the spin base 21.

Also, in the preferred embodiment described above, nitrogen gas issprayed from the two-fluid nozzle 60 onto the outer upper surface 43 dof the processing cup 40. Meanwhile, a gas to be sprayed may be an inertgas of a different type (such as argon (Ar)), or gas other than an inertgas (such as air).

A substrate to be processed by the substrate processing apparatus 1 isnot limited to a semiconductor substrate, but it may also be a glasssubstrate used in a flat-panel display such as a liquid crystal display.

While the invention has been shown and described in detail, theforegoing description is in all aspects illustrative and notrestrictive. It is therefore understood that numerous modifications andvariations can be devised without departing from the scope of theinvention.

What is claimed is:
 1. A method of cleaning a substrate processingapparatus that performs substrate processing with a processing solution,the method comprising the step of: (a) causing a substrate holdingelement to rotate at a first number of revolutions, said substrateholding element having a holding surface facing the lower surface of asubstrate to be held on said substrate holding element, and at the sametime, supplying a cleaning solution from a cleaning solution supplynozzle onto said holding surface while placing the upper end of a cupsurrounding said substrate holding element below said substrate holdingelement, thereby cleaning an outer upper surface of said cup with saidcleaning solution scattered from said holding surface while said holdingsurface is rotating, wherein in said step (a), said cleaning solutionsupply nozzle for supplying said cleaning solution is caused to moveover said holding surface, so that said cleaning solution scattered fromsaid holding surface falls on different positions of said outer uppersurface of said cup.
 2. The method according to claim 1, wherein, insaid step (a), said cleaning solution supply nozzle is caused to moverepeatedly between one edge and an opposite edge in a direction of thediameter of said holding surface.
 3. The method according to claim 2,wherein, in said step (a), said cleaning solution supply nozzle performsan intermittent reciprocating movement in which said cleaning solutionsupply nozzle moves to said opposite edge and stops for a while afterstopping at said one edge for a while, and then moves back to said oneedge and stops for a while.
 4. The method according to claim 1, furthercomprising the step of: (b) causing said substrate holding element torotate at a second number of revolutions higher than said first numberof revolutions, and at the same time, supplying a cleaning solution fromsaid cleaning solution supply nozzle onto said holding surface, therebycleaning an area outside said cup and surrounding said cup with saidcleaning solution scattered from said holding surface while said holdingsurface is rotating.
 5. The method according to claim 4, furthercomprising the step of: (c) causing said substrate holding element torotate at a third number of revolutions smaller than said first numberof revolutions, and at the same time, supplying a cleaning solution fromsaid cleaning solution supply nozzle onto said holding surface whileplacing the upper end of said cup above said substrate holding element,thereby cleaning the inner side of said cup with said cleaning solutionscattered from said holding surface while said holding surface isrotating.
 6. The method according to claim 5, further comprising thestep of: (d) drying said outer upper surface of said cup and said areaoutside said cup with airflow generated by causing said substrateholding element to rotate at a fourth number of revolutions higher thansaid second number of revolutions.